FIGS. 1A and 1B are diagrams illustrating the configuration of a system including a computer and a display. In FIG. 1A, a computer 1A outputs an analog image signal (e.g. an analog RGB signal) to a display 2A (e.g. a LCD (Liquid Crystal Display)) via an analog signal cable 3. The deterioration of a signal level and the deviation of display timing (i.e., the deviation of sampling timing when digital sampling of the analog image signal is performed) occur in the analog image signal due to a loss in a transmission path. Such a deterioration of the signal level and such a deviation of the display timing directly influence an image quality, and the blur, the flicker and the deviation of the image occur. To correct the blur, the flicker and the deviation of the image, the display 2A includes an image quality adjustment function.
In FIG. 1B, the computer 1A outputs a digital image signal (e.g. a DVI (Digital Visual Interface) signal or a HDMI (trade mark) (High-Definition Multimedia Interface) signal) to a display 2B (e.g. the LCD) via a digital signal cable 4. In the transmission of the digital image signal, the computer 1A also transmits information on a field angle to the display 2B, and therefore the blur, the flicker and the deviation of the image which influence the image quality do not occur. For this reason, the display 2B does not include the image quality adjustment function.
FIGS. 2A and 2B are diagrams illustrating the configuration of a system including computers, the display and a KVM switch. In FIG. 2A, a KVM switch 5A (e.g. an analog KVM switch) selects a computer to be connected to the display 2A from computers 1A to 1D. An analog image signal from the selected computer is output to the display 2A via the KVM switch 5A and an analog signal cable 6. In this case, the deterioration of the signal level and the deviation of the display timing occur due to the loss in the KVM switch 5A and the analog signal cable 6. However, the display 2A includes the image quality adjustment function, and the display 2A therefore can adjust the image quality of the analog image signal to be displayed.
However, when the KVM switch 5A is used, a plurality of transmission paths exist between the computers 1A to 1D and the display 2A. On the contrary, the display 2A includes only an adjustment value for performing the image quality adjustment corresponding to a single transmission path. Therefore, whenever the KVM switch 5A switches the computer, an operator needs to adjust the image quality of the analog image signal with the use of the image quality adjustment function of the display 2A.
In FIG. 2B, a KVM switch 5B (e.g. a digital KVM switch) selects a computer to be connected to the display 2B from the computers 1A to 1D. A digital image signal from the selected computer is output to the display 2B via the KVM switch 5B and a digital signal cable 7. In this case, each of the computers 1A to 1D transmits the information on the field angle in addition to the digital image signal to the display 2B, and therefore the blur, the flicker and the deviation of the image which influence the image quality do not occur. For this reason, the display 2B does not include the image quality adjustment function.
Moreover, there has been conventionally known a KVM switch that receives a reference signal and adjusts the distortion of a video signal (e.g. see Patent Document 1).